Tensioning device

ABSTRACT

A tensioning device, adapted for use with a station in which web material is unwound from a roll, has a current-to-pneumatic pressure converter which is responsive to the current drawn by the armature of a motor associated with a tension multiplier connected in line with the web drawn from the roll. The pneumatic pressure determined by the current-to-pressure converter is adapted to control pneumatic brakes operative to brake the unwinding speed of the roll. A preset pressure operates the pneumatic brakes prior to initiation of the system, and this preset pressure is replaced by the pressure determined by the current-to-pressure converter, as soon as the motor current increases to a predetermined level.

United States Patent 1191 Wentworth 1 TENSIONING DEVICE [75] Inventor: William 11. Wentworth, Rockford,

Ill.

[73] Assignee: Beloit Corporation, Beloit, Wis.

[22] Filed: Dec. 6, 1972 [21] App]. No.: 312,506

' [52] US. Cl... 242/7544, 226/39, 242/75.2, 318/6 [51] Int. Cl B65h 25/22, B65h 23/10 [58] Field of Search 242/7543, 75.44, 75.45,

[56] References Cited UNITED STATES PATENTS 1 2,983,463 5/1961 Aaron et a1 242175.43 3,018,978 1/1962 Graneau et al. 242/7551 3,049,313 8/1962 Jordan et a1. 242/75.44

3,071,300 l/1963 Justus 242/7543 X 3,081,961 3/1963 Kron 242/75.47

. 3,127,292 3/1964 Early 242/7551 X 3,257,086 6/1966 Drenning 242/7547 X Dec. 10, 1974 11/1968 Tison et al 226/39 X FOREIGN PATENTS OR APPLICATIONS 6/1969 Great Britain 242/75.44

Primary Examiner-John W. Huckert Assistant ExaminerJohn M. Jillions Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson 57 I ABSTRACT A tensioning device, adapted for use with a station in verter is adapted to control pneumatic brakes operative to brake the unwinding speed of the roll. A preset pressure operates the pneumatic brakes prior to initiation of the system, and this preset pressure is replaced by the pressure determined by the current-to-pressure converter, as soon as the motor current increases to a predetermined level.

10 Claims, 1 Drawing Figure RE LAY TENSIONING DEVICE BACKGROUND OF THE INVENTION material as it is unwound, because the diameter of the roll changes as the material is unwound. The diameter is a maximum initially, and decreases to aminimum as the operation progresses. The torque, which acts on the core supporting the roll, and which is developed as a result of pulling the web material from the core, also changes as the operation progresses.

In the prior art, brake mechanismshave been employed for placing a predetermined braking torque on the roll-supporting core, and the amount of torque applied by such brake mechanism is reduced as the web material is withdrawn from the roll, in order to hold the tension constant. However, when the core which supports the roll is made of relatively light material such ascardboard, or thelike, the amount of torque which must be used in order to achieve the desired web ten.- sion issometimesgreater thanthe core material can stand, so that the results are unsatisfactory. It is, therefore. desirable to providea system formaintaining the web material under the proper tension as it is withdrawn from the roll, while applyinga smaller torque to the core of the roll.

SUMMARY or THE INVENTION It is a principal object of the present invention to provide apparatus for tensioning the 'web material as it is withdrawn from a supply roll, without applying large values of torque to'the roll.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, a supply roll. 'is illustrated, which comprises a quantity of web material 14 supported on a core 12 and adapted for use in any process which employs web material. The web material 14 is withdrawn from the roll 10 and passed around a S-wrap tension multiplier 16 and then on to the processing apparatus (not shown). The function of the S- wrap tension multiplier 16 is to multiply thetension of the web so that the web 14 downstream from the tension multiplier'has a greater value than that on the web 14 upstream therefrom; The processing apparatus contains as a part thereof a driven reel or the like for pull.- ing the web 14 through the processing apparatus from the supply roll 10, and it acts as a source of tension for the web 14.

The tension multiplier 16 incorporates a pair of rollers 18 and 20 supported for rotation on'shafts19 and, 21, and geared together by gear means (not shown) so that both rotate together in unison. The shaft 21 of the roller 20 is connected to the shaft of a motor 24, for rotation therewith, the connection being illustrated by the dashed line 25. The geared connection between the rollers 18 and 20 causes the roller 18 to also rotate with the motor 24. The motor 24 is energized in a direction so as to tend to turn the. roller 20 in a direction opposite to the direction of movement of the web 14. The connection between the rollers 18 and 20 causes the roller 18 to also be urged in the direction opposite to the di rection of travel of the web. Thus, the current which flows through the armature winding of the-motor is proportional to the torque on the motor shaft. As the torque on the motor shaft is directly proportional to the tension of the web 14, the armature current of the motor24 is a direct index of the tension of the web 14.

Another object of the present invention is to construct such apparatus of readily available'components.

Theseand other objects and advantages of the present invention will become manifest upon an inspection of the following description and the accompanying drawings. I I I In one embodiment of the present invention there is provided a tension multiplier interposed in the path of the web from a supply roll to-apparatus which pulls the web from the roll, a motor connected to said tension multiplier and adapted to urge the web toward the roll toincreasethe tension of the web downstream from said tension multiplier, a current-to-pressure converter connected with the motor and responsive to the current drawn thereby for producing a pneumatic pressure, and

brake means connected with said supply roll, the brake BRIEF DESCRIPTION OF THE DRAWING Reference will now be made to the accompanying drawing, which illustrates, in functional block diagram form, an illustrative embodiment of the present invention.

The armature of the motor 24 is connected to a pair of terminals 26, and a resistor 28 is connected in series with the armature winding and the terminals 26. Accordingly, the armature current flows through the resistor'28, and the voltage drop thereacross is proportional to the armature current. The terminals 26 may be connected to a resistance external tothe circuit, or, alternatively, to a source of voltage. The external network connected to the terminals 26 is selected to give the desired performance of the motor 24 inconjunction with the resistor 28. The resistor 28 is sized to produce a desired magnitude of voltage drop thereacross in response to the desired armature current, which of course depends upon the desired tension for the web 14, and the particular characteristics of the motor 24.

-A transducer 30 has a pair of input terminals connected across the resistor 28 and is responsive to the 'voltage dropthereacross to regulate the value of pressure on a pneumatic output line 32. An input line 34 is connected from the transducer 30 to a source 36 of air pressure. The pressure of the source 36 is greater than that desired on the output line 32, so the transducer 30 A rheostat 38 is connected in parallel with the input terminals of the transducer 30, and is adjusted to select a given pressure output from the transducer 30 for a given value of armature current. Therefore, the rheostat 38 is conveniently employed to establish a scale factor between armature current and the pressure on the output line 32.

The output line 32 is connected through a valve 40 to an air brake 42'which is mechanically coupled to the shaft on which the core 12 is supported. The mechanical coupling is illustrated by means of a dashed line 44 which interconnects the brake 42 and the core 12. In operation, the valve 40 is normally in the condition schematically illustrated in the drawing, so that the pressure on the output line 32 is conveyed directly to the brake 42 to establish the torque supplied by the brake 42 on the core 12. The greater that this torque is, the greater is the tension of the web 14 as it is withdrawn from the roll 10. As already described, however, this tension is less than the tension on the web 14 downstream from the tension multiplier 16. Accordingly, a

I thereacross to control a solenoid 48 for operating the valve 40. When the voltage drop across the resistor 28 exceeds the threshold level of operation of the relay 46, it energizes the solenoid 48 via lines 50 and 52. The

valve 40 is then operated to interconnect the line 32 and the brake 42.

During the initial period of operation, when the processing apparatus is starting up, there is substantially no tension on the web 14, and, accordingly, no current through the armature winding of the motor 24, so the relay 46 and the solenoid 48 are both unactuated. When the solenoid 48 is not actuated, the valve 40 connects the brake 42 to a line 54 which is connected to the'pressure source 36 through a pressure reducer 56. The pressure reducer 56 is preferably a manually controlled pressure reduction valve which selects a predetermined constant pressure on the line 54, less than that produced by thesource 36. Such valves are well known in the art and therefore need not be specifically described herein. This pressure is supplied to the brake 42, through the unoperated valve 40, so that the brake 42 applies a predetermined'braking force to the core 12 during the initial period while the tension on the web 14 is building up from zero to its operating value. When the processing apparatus is started up, the tension of the web 14 increases, and armature current of the motor 24 increases, resulting in a voltage drop across the resistor 28. When this reaches a value just less than the value which corresponds to the working tension on the web '14, the relay is operatedso as to connect the brake 42 to the regulated output 32 of the transducer 30. In this way the tension on the web 14 is caused to be raised quickly and smoothly to its operatingvalue as the processing apparatusflis started up, and

the transducer 30 and the valve 40 thereafter control the brake 42 to thereafter control the tension on the web-l4. r Y

As the web material l4'is withdrawn from the roll 10, the necessary torque-applied by the brake 42, in order to produce a predetermined tension on the web 14, decreases, because of the reducing diameter of the roll 10. The apparatus of the present invention is operative to sense, by means of the current flowing through the armature of the motor 24, the condition of the roll 10, and adjust the value of the pneumatic pressure supplied to the brake 42 accordingly.

The motor 24 is preferably a shunt motor, the field of which is constantly energized by means of a source of d.c. potential (not shown). Alternatively it may be a series or universal motor. An alternating current motor may alternatively be employed, and in that event, means for rectifying the ac. armature current is employed.

It will be appreciated that it is necessary that the rollers l8 and 20 be equipped with a surface having a sufficiently large coefficient of friction when employed with the web material 14 so as to achieve the desired tension without the web material 14 slipping relative to the surface of the rollers.

What is claimed is:

l. A tensioning device for use with a process employ ing a quantity of web material drawn from a supply roll comprising, in combination, a roller mounted on a shaft, said web contacting the surface of said roller between said supply roll and said processing apparatus, a motor connected to said shaft, means for sensing the armature current of said motor and for regulating the pneumatic pressure on an output line in response thereto, brake means connected with said output line and adapted for impeding the rotating of said supply roll to control the tension on said web, and a source of potential connected to the 'motor to urge said motor to rotate in a direction opposite to the direction of travel of the web.

2. Apparatus according to claim 1, including manually operated means for controlling the scale factor between thearmature current of said motor, and the pressure on said output line.

3. Apparatus according to claim 1 including means for establishing a predetermined pneumatic pressure. and means operative during an' initial period of withdrawing said web from said roll while said tension is low for connecting said brake means to said predetermined pressure means.

4. Apparatus according to claim 1 wherein said brake means is operatively associated with the core upon which said supply roll is supported and is operative in response to the pressure on said output line to impede the rotation of said core when the tension of said web is less than a predetermined value.

5. Apparatus according to claim 1, wherein said roller guides said web around a turn, whereby said web is in frictional contact with the surface of said roller as it passes throughsaid turn.

6. Apparatus according to claim 1, including a second roller connected to the first said roller for rotation therewith, said web contacting the surface of said second roller, whereby said first and second rollers are in frictional contact with said web.

7. Apparatus according to claim 6, including means for supporting said rollers to permit said web to define an S shape as it traverses said two rollers.

8. Apparatus according to claim 1, wherein said motor is a d.c. motor, and wherein said source of potential is connected in series with said armature to urge said motor to rotatein the direction opposite to the direction of travel of said web.

9. Apparatus according to claim 8, including a resistor in series with the armature of said motor, and means for connecting said sensing means across said resistor.

10. Apparatus according to claim 3, including relay means connected to said motor and responsive to the armature current thereof for operating a'valve at the mined pressure means from said brake means and to connect said output line to said brake means. 

1. A tensioning device for use with a process employing a quantity of web material drawn from a supply roll comprising, in combination, a roller mounted on a shaft, said web contacting the surface of said roller between said supply roll and said processing apparatus, a motor connected to said shaft, means for sensing the armature current of said motor and for regulating the pneumatic pressure on an output line in response thereto, brake means connected with said output line and adapted for impeding the rotating of said supply roll to control the tension on said web, and a source of potential connected to the motor to urge said motor to rotate in a direction opposite to the direction of travel of the web.
 2. Apparatus according to claim 1, including manually operated means for controlling the scale factor between the armature current of said motor, and the pressure on said output line.
 3. Apparatus according to claim 1 including means for establishing a predetermined pneumatic pressure, and means operative during an initial period of withdrawing said web from said roll while said tension is low for connecting said brake means to said predetermined pressure means.
 4. Apparatus according to claim 1 wherein said brake means is operatively associated with the core upon which said supply roll is supported and is operative in response to the pressure on said output line to impede the rotation of said core when the tension of said web is less than a predetermined value.
 5. Apparatus according to claim 1, wherein said roller guides said web around a turn, whereby said web is in frictional contact with the surface of said roller as it passes through said turn.
 6. Apparatus according to claim 1, including a second roller connected to the first said roller for rotation therewith, said web contacting the surface of said second roller, whereby said first and second rollers are in frictional contact with said web.
 7. Apparatus according to claim 6, including means for supporting said rollers to permit said web to define an S shape as it traverses said two rollers.
 8. Apparatus according to claim 1, wherein said motor is a d.c. motor, and wherein said source of potential is connected in series with said armature to urge said motor to rotate in the direction opposite to the direction of travel of said web.
 9. Apparatus according to claim 8, including a resistor in series with the armature of said motor, and means for connecting said sensing means across said resistor.
 10. Apparatus according to claim 3, including relay means connected to said motor and responsive to the armature current thereof for operating a valve at the end of said initial period when said armature current exceeds a predetermined level, said valve being interposed in the path between said output line and said brake means and operable to disconnect said predetermined pressure means from said brake means and to connect said output line to said brake means. 